Author
Topic: Blackening (Read 7874 times)

first foray into blackening was almost a success, its good enough at least. The body was the last bit I did and seems to be the best finish this was done by setting my furnace to 360C and applying linseed oil once at temp then blowing excess oil away and then reheating till black.I have put the worst bits in the final pic because I would welcome any input to make a better job next time I try.

HiThe method I have been using is to heat until red hot and drop into used diesel engine oil (lots of carbon) Be aware that the clouds of oil vapour are able to ignited from the red hot metal or any naked flame in the vicinity of the jobThis becomes critical if doing a long run of parts and the oil gets very hot so be prepared for fire fighting

I guess time will tell but I didnt heat until red hot but my home built electric furnace lets me set the temperature to whatever I want within reason I may up the temperature a little the next time and clean the part more thoroughly. It would be nice to get a formula I know for certain is going to give me good results rather than good enough.I think blowing the excess oil off the piece helped a lot, I didnt do it with the first few bits and it seemed to me that where the oil pooled it formed a crust which stopped the metal under it from turning and the two top rings I actually cleaned off and redid.

Logged

Turns out this life c**p is just one big distraction from death but a good one. For the love of god dont give yourself time to think.https://myshedblog.wordpress.com/

None of these process' compare to the nitrate black you get on things like good machine tooling. Sadly, the chemical brew you need for that is nasty, even by my standards...Parkorising (phosphate coating) isn't bad or hard to do and is commonly used on guns. Higher concentrations of phosphoric acid are tricky get in my part of the world though..

The guy in the link used a regular battery to get his manganese (and some zinc, which would explain his grey-ish result). Concentrated phosphoric acid is easy to obtain in the UK - just look on eBay, or buy direct from one of the companies. I presume Manganese Dioxide is also easy to get although I've never tried.

Logged

Cheers!Ade.--Location: Wallasey, Merseyside. A long way from anywhere.Or: Zhengzhou, China. An even longer way from anywhere...Skype: adev73

it's hard to get consistent with homebrewed mixtures and not all of the scrabnioum iron ore metals take the finish equally well.

Pekka

In the link he says " Now you are ready to start the Parkerising process, pour the mixture in a stainless steel pot or pan of suitable size, obviously an old one that is not going to be used for cooking again, put a small piece of steel wool (about the size of a marble) in the mixture and bring it to boiling point. "Why would the steel wool be needed?

Yup, if you don't "bait" it with wire wool it will etch couple of first batch and then starts parkerizing. Note also that pretty much all of the wire wool you buy is rustproofed with oil....oil is best to be removed or it will not work.

My experience is that you need somewhat more than on that instruction....I found somewhere grams and when I weighted the amount of dry wire wool, it was a good tuft, more of a "hand" than a pinch for a two litres of park. In industrial setup on old times the amount of chemicals were pretty small, but temperature was pretty well controlled, whereas on the majority of the writeups temprerature was described from simmering to rolling boil, worst case nearly 30 degree variation, which seems way too random for this process.

It just so happens that I kept the example that was pictured in the Oct. 2013 thread as mentioned in Tom Ossleton's post ^^ up here.It has been kicking around my workshop for the past few years, during this time it has only been oiled (WD 40) once.I don't think it's done too bad as most steel in my place manages to develop surface rust in a matter of a few weeks. If it had been oiled on a fairly regular basis I'm sure it would still be as good as new.The second pic is the fresh item and the following are as it is now.Regards, Dave